Fossil fuel extraction systems produce extraction fluid by combining at least fresh water with viscosity modifiers. An extraction system injects this fluid into a well. Subsequent to injection, a fluid containing at least fresh water returns to the surface as produced water. The system collects the produced water, recycles the water via distillation, and combines the distilled water with fresh water and viscosity modifiers to form more extraction fluid. Distillation yields water of high purity, but also adds substantial costs to the extraction system.